The present invention relates generally to miniaturized incandescent lamps, and more particularly to a silicon-filament, vacuum-sealed incandescent light source.
Miniaturized incandescent lamps were reported for use in displays in the 1970's. See P.M. Alt, "Performance and design considerations of the thin-film tungsten matrix display," IEEE Trans. Electron Devices, vol ED-20, pp 1006-1015, Nov. 1973; and F. Hochberg, H.K. Seitz, and A.V. Brown, "A thin-film integrated incandescent display" , IEEE Trans. Electron Devices, vol ED-20, pp. 1002-1005, Nov. 1973. These devices, which consisted of thin-film tungsten filaments suspended from a glass substrate, were fabricated using hybrid circuit technology. More recently, miniature incandescent light sources have been fabricated utilizing silicon integrated circuit (IC) technology. See H. Guckel and D.W. Burns,"Integrated transducers based on blackbody radiation from heated polysilicon films", Transducers' 85, pp. 364-366, Jun. 11-14, 1985; and G. Lamb, M. Jhabvala, and A. Burgess, "Integrated-circuit broadband infrared source", NASA Tech. Briefs, p. 32, Mar. 1989. In this later work, the incandescent element was an electrically-heated polycrystalline-silicon microbridge resistor elevated a few micrometers above a silicon substrate and exposed to air. Guckel et al. demonstrated the use of this device to make an all-silicon optical coupler.
Even though the polysilicon filaments described in Guckel et al. and Lamb et al are capable of high temperature operation, they are not isolated from the environment, and therefore are susceptible to particle contamination or possibly to damage caused by physical contact. In addition, the useful device life-time is limited by oxidation of the exposed silicon filament when operated in free air. Guckel et al. suggested that the lifetime could be increased if the filaments were coated with silicon nitride to reduce their rate of oxidation.
In view of the foregoing, an object of the present invention is to provide a microlamp in which oxidation and contamination problems are substantially eliminated.
More specifically, an object of the present invention is to provide a vacuum-sealed microlamp.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the claims.